Keep track of multiple layout roots

Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
@@ skipping 84 matching lines @@
     void setContentsSize(const IntSize&);
     IntPoint clampOffsetAtScale(const IntPoint& offset, float scale) const;
 
     void layout();
     bool didFirstLayout() const;
     void scheduleRelayout();
     void scheduleRelayoutOfSubtree(LayoutObject*);
     bool layoutPending() const;
     bool isInPerformLayout() const;
 
-    LayoutObject* layoutRoot(bool onlyDuringLayout = false) const;
-    void clearLayoutSubtreeRoot() { m_layoutSubtreeRoot = nullptr; }
+    bool isLayoutRoot(const LayoutObject&) const;
+    void clearLayoutSubtreeRoot(const LayoutObject*);

[Julien - ping for review, 2015/02/27 16:38:09]

Should we also use a reference here for API coherency? (we also don't expect
nullptr)

     int layoutCount() const { return m_layoutCount; }
 
+    void countObjectsNeedingLayout(unsigned& needsLayoutObjects, unsigned& totalObjects, bool& isPartial);
+
     bool needsLayout() const;
     void setNeedsLayout();
 
     void setNeedsUpdateWidgetPositions() { m_needsUpdateWidgetPositions = true; }
 
     // Methods for getting/setting the size Blink should use to layout the contents.
     IntSize layoutSize(IncludeScrollbarsInRect = ExcludeScrollbars) const;
     void setLayoutSize(const IntSize&);
 
     // If this is set to false, the layout size will need to be explicitly set by the owner.
@@ skipping 201 matching lines @@
 
     IntSize scrollOffsetForViewportConstrainedObjects() const;
 
     // Override scrollbar notifications to update the AXObject cache.
     virtual void didAddScrollbar(Scrollbar*, ScrollbarOrientation) override;
     virtual void willRemoveScrollbar(Scrollbar*, ScrollbarOrientation) override;
 
     // FIXME: This should probably be renamed as the 'inSubtreeLayout' parameter
     // passed around the FrameView layout methods can be true while this returns
     // false.
-    bool isSubtreeLayout() const { return !!m_layoutSubtreeRoot; }
+    bool isSubtreeLayout() const { return !m_layoutSubtreeRoots.isEmpty(); }
 
     // Sets the tickmarks for the FrameView, overriding the default behavior
     // which is to display the tickmarks corresponding to find results.
     // If |m_tickmarks| is empty, the default behavior is restored.
     void setTickmarks(const Vector<IntRect>& tickmarks) { m_tickmarks = tickmarks; }
 
     // Since the compositor can resize the viewport due to top controls and
     // commit scroll offsets before a WebView::resize occurs, we need to adjust
     // our scroll extents to prevent clamping the scroll offsets.
     void setTopControlsViewportAdjustment(float);
@@ skipping 266 matching lines @@
         TemporaryChange<bool> m_scope;
     };
 
 private:
     explicit FrameView(LocalFrame*);
 
     void dispose() override;
     void reset();
     void init();
 
+    void clearLayoutSubtreeRootsAndMarkContainingBlocks();
+
     // Called when our frame rect changes (or the rect/scroll position of an ancestor changes).
     virtual void frameRectsChanged() override;
 
     friend class LayoutPart;
 
     bool contentsInCompositedLayer() const;
 
     void applyOverflowToViewportAndSetRenderer(LayoutObject*, ScrollbarMode& hMode, ScrollbarMode& vMode);
     void updateOverflowStatus(bool horizontalOverflow, bool verticalOverflow);
 
     void updateCounters();
     void forceLayoutParentViewIfNeeded();
     void performPreLayoutTasks();
-    void performLayout(LayoutObject* rootForThisLayout, bool inSubtreeLayout);
+    void performLayout(bool inSubtreeLayout);
     void scheduleOrPerformPostLayoutTasks();
     void performPostLayoutTasks();
 
     void invalidateTreeIfNeeded();
 
-    void gatherDebugLayoutRects(LayoutObject* layoutRoot);
-
     DocumentLifecycle& lifecycle() const;
 
     void contentRectangleForPaintInvalidation(const IntRect&);
     virtual void contentsResized() override;
     void scrollbarExistenceDidChange();
 
     // Override Widget methods to do point conversion via renderers, in order to
     // take transforms into account.
     virtual IntRect convertToContainingView(const IntRect&) const override;
     virtual IntRect convertFromContainingView(const IntRect&) const override;
@@ skipping 78 matching lines @@
     RefPtrWillBeMember<LocalFrame> m_frame;
 
     WebDisplayMode m_displayMode;
 
     bool m_doFullPaintInvalidation;
 
     bool m_canHaveScrollbars;
     unsigned m_slowRepaintObjectCount;
 
     bool m_hasPendingLayout;
-    LayoutObject* m_layoutSubtreeRoot;
+    HashSet<LayoutObject*> m_layoutSubtreeRoots;
 
     bool m_layoutSchedulingEnabled;
     bool m_inPerformLayout;
     bool m_inSynchronousPostLayout;
     int m_layoutCount;
     unsigned m_nestedLayoutCount;
     Timer<FrameView> m_postLayoutTasksTimer;
     Timer<FrameView> m_updateWidgetsTimer;
     bool m_firstLayoutCallbackPending;
 
@@ skipping 113 matching lines @@
     static const unsigned visualPixelThreshold = 32 * 32;
     if (m_visuallyNonEmptyPixelCount > visualPixelThreshold)
         setIsVisuallyNonEmpty();
 }
 
 DEFINE_TYPE_CASTS(FrameView, Widget, widget, widget->isFrameView(), widget.isFrameView());
 
 } // namespace blink
 
 #endif // FrameView_h